The present disclosure relates to a battery unit, a battery module, a power storage system, an electronic device, a power system, and an electric vehicle.
Lithium ion secondary batteries that use carbon for a negative electrode, a lithium-transition metal composite oxide for a positive electrode, and a carbonate mixture for an electrolyte have been widely known for some time. In a lithium ion secondary battery having such a configuration, since the carbonate is stable to the oxidation and reduction of water and other organic solvents and can obtain a higher voltage, a larger energy density and a higher capacity can be obtained than for a nickel-hydrogen battery, which is an water-based battery. Consequently, lithium ion secondary batteries are becoming widely spread as a secondary battery for power tools, laptop computers, mobile phones, video cameras, digital still cameras and the like.
Recently, lithium ion secondary batteries have started to spread into applications other than those mentioned above, even into industrial uses for electric vehicles, power storage and the like. Industrial secondary batteries need to have high capacity, high power output, and long life battery qualities. One of the battery qualities required in order to withstand high current is heat-release properties. When a high current is applied, heat is generated. However, an excessive increase in battery temperature is known to accelerate degradation of battery performance, and shorten battery life. Accordingly, how efficiently the heat generated by the battery can be released becomes important. This issue is now the subject of various studies.
For example, the following Patent Literature 1 discloses a configuration of a lithium ion battery for a vehicle, in which when four lithium ion batteries are stacked, a metal heat sink that has been subjected to an insulating treatment is arranged between each of the batteries, and the lithium ion batteries, the heat sink, and an end plate are clamped together by a clamping belt.